4-bit relay adder

For years, I have had a dream of building a computer entirely out of electromechanical relays, but I have always been too busy. Recently, I have had a lot of time on my hands, so I decided to start designing it. Ten hours, 36 SPDT relays, and countless wires later, I ended up with this contraption. It is capable of adding four bit numbers, and it actually gives the right answer. I know it isn’t the 8-bit, turing complete CPU of my dreams, but it’s a start. Once I snag a deal on some 4PDT relays, the real fun will begin.